With respect to the distributing wires required when fabricating a semiconductor element (such as an LSI or IC element or the like), it is common that a barrier and/or adherent layer as a primary coat in or on contact holes and grooves which permit the connection between lower and upper distributing wires. This barrier layer has frequently been formed, between layers of a wire material and an insulating material, for the purpose of preventing any mutual diffusion between the wire material and the insulating material and hence preventing the occurrence of any deterioration of the characteristic properties of such a semiconductor element, while the adherent later has likewise frequently been formed, between layers of a wire material and an insulating material, for the purpose of preventing any peeling of films at the boundary between the layers of the wire material and the insulating material.
There has recently been proposed the use of a copper material having a lower specific resistance as a material for forming distributing wires within contact holes and/or grooves, in place of the conventionally used Al materials. In this case, a barrier layer is formed between copper distributing wires and a silicon oxide film or the like, in order to prevent any diffusion of copper into an insulating layer consisting of, for instance, a silicon oxide film serving as a primary coat for the copper distributing wires.
Incidentally, there has conventionally been used the plating technique in the formation of such copper distributing wires described above. However, the size of contact holes or the like has become longer and narrower as the reduction of the scale of the distributing wires of, for instance, LSI elements, and an additional problem arises, such that it would be difficult for a plating solution to penetrate into even the deep depth or interior of, for instance, such long and narrow contact holes having such a high aspect ratio. Accordingly, this makes the formation of copper distributing wires from such a plating solution, quite difficult.
For this reason, there has been investigated, under the existing circumstances, a method which makes use of a gas, represented by the CVD technique as a substitute for the plating technique, as a means for forming copper distributing wires.
In the copper distributing wire-forming process, which makes use of the CVD technique, however, the formation of the copper film is greatly affected by the surface characteristic properties of the material used for forming a primary coat and more specifically, the process suffers from various problems in that (1) it is difficult to form initial nuclei and it takes a long period of time to form such initial nuclei; and (2) the film is apt to undergo the so-called island-like growth. Accordingly, it would be quite difficult to form a continuous film by the use of the foregoing process. For this reason, when the hole diameter: φ is not more than 0.2 μm and the width of the groove is not more than 0.2 μm and when the aspect ratio of these holes and/or grooves is not less than 4, the filling of, for instance, a hole would be accompanied by the formation of voids and accordingly, it would in fact be difficult to completely fill such a hole or the like. Thus, any CVD technique cannot be used for filling holes or grooves each having a diameter of not more than 0.1 μm, whose filling by the plating technique becomes difficult and this would result in a serious problem in the future.
The process likewise suffers from a problem in that it is difficult to ensure any excellent adhesion between the copper-containing film formed through the CVD technique and a barrier layer or the like.
The formation of a continuous film according to the CVD technique requires the acceleration of the nuclei-forming rate at the initial step of a film-forming process and an increase of the density of nuclei thus formed and accordingly, the role of a barrier layer (adherent layer) used as the primary coat would become quite important. At the same time, it is likewise important to ensure good adhesion between the barrier layer (adherent layer) and the copper-containing film for the formation of copper distributing wires.
When using a copper film formed according to the CVD technique as distributing wires, there has been known a method which comprises the steps of forming, in advance, a vanadium nitride film according to the reactive sputtering technique or the CVD technique and then growing a film of a copper material on the vanadium nitride film by the CVD technique to thus form a barrier layer having good adhesion to the copper film and having a small internal stress (see, for instance, Patent Document 1 specified later). In this case, bis(cyclopenta-dienyl) vanadium(III) is, for instance, used as a raw material for forming a barrier layer, but any satisfactory barrier layer has not always been prepared. Moreover, there has been used known materials such as (hexafluoro-acetyl acetonato) copper(I) trimethyl vinyl silane [Cu(hfac)(tmvs)] as the raw materials for forming copper-containing films, but the hole is not always completely filled therewith when the diameter of the hole is small, under the existing circumstances. This would possibly be resulted from the characteristic properties of the primary coat.
The conventionally used Cu(hfac)(tmvs) described above suffers from additional problems such that any desired copper-containing film cannot be prepared in good reproducibility (any stable filling of, for instance, holes cannot be ensured when the size of the opening of the hole: φ is not more than 0.2 μm and when the aspect ratio is not less than 4), which would possibly be resulted from the characteristic properties of the primary coat, and that voids are generated due to the annealing treatment after the step of filling the holes or the like.
FIGS. 6 and 7 schematically show voids possibly generated when a copper-containing film is formed according to the conventional techniques. More specifically, FIG. 6 shows the voids generated when copper distributing wires are formed by applying a conventional copper-containing film on a conventional barrier layer to thus fill holes or the like present thereon with the same, while FIG. 7 illustrates the conditions of voids generated during the annealing treatment carried out after the conventional step of forming copper distributing wires.
When forming copper distributing wires, the foregoing problems would arise and accordingly, the conventional techniques would never produce any LSI element provided with highly reliable distributing wires. Thus, one of the causes for this would be believed to be the instability of the raw materials typical of the Cu(hfac)(tmvs) complex described above and for this reason, there has been desired for the development of a raw material for forming copper-containing film, which is excellent in hole- or groove-filling properties and which can satisfy other characteristic properties as well.
Moreover, there have likewise been known special copper complexes as raw materials for forming copper-containing films according to the CVD technique (see, for instance, Patent Document 2 specified below). When using the copper complex, however, there are many problems remaining unsolved. For instance, any condition required for forming a desired copper-containing film has not yet been elucidated.    Patent Document 1: Japanese Un-Examined Patent Publication 2003-17437 (Claims);    Patent Document 2: Japanese Un-Examined Patent Publication 2003-292495 (Claims).